1. Field of the Invention
The present invention relates to a peer to peer (P2P) type information delivery system including a plurality of node devices connected with each other through a communication network, and particularly relates to a technical field for a non-participant node device of participating in an overlay network formed by participation of all or part of the plurality of node devices.
2. Discussion of the Related Art
In a peer to peer type information delivery system, for example, in an overlay network constructed by use of a distributed hash table (hereinafter referred to as DHT), every node device does not recognize link information to all the node devices participating in the overlay network (for example, IP addresses) but retains only link information to some node devices which is acquired upon participation, and data inquiry or the like is performed based on such link information.
In such an overlay network, even when participation and withdrawal by a node device occur frequently, load distribution must be done appropriately. There is disclosed in the Non-patent Document 1, a technique of appropriately distributing load when participation and withdrawal into/from an overlay network occur frequently. Non-patent Document 1: “Consideration on Lightweight Load Balancing for Distributed Hash Tables”, Technical Report of the Institute of Electronics, Information, and Communication Engineers.